Erasable recording material capable of inputting additional information written thereon and information recording system and information recording method using the recording material

ABSTRACT

An erasable recording material including a substrate, and an erasable recording layer which is formed overlying the substrate and in which image information is repeatedly recorded and erased, and optionally includes an undercoat layer formed between the substrate and the recording layer, a protective layer formed overlying the recording layer and an intermediate layer formed between the recording layer and the protective layer, wherein the erasable recording material further includes one or more markers which are used for inputting image information additionally written on the recording material. An information recording system and method are also provided in which additional information written on the erasable recording material, in which image information is previously recorded, is incorporated to the previously recorded image information.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.09/470,959, filed Dec. 22, 1999 (now U.S. Pat. No. 6,432,518.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an erasable recording material having amarker, in which image information can be reversibly recorded and erasedand to which additional information written on the recording materialcan be added to the image information using the marker, and to aninformation recording system and an information recording method usingthe recording material.

2. Discussion of the Related Art

Recently, a huge amount of paper is used and disposed of, and there areserious social problems as to how to treat the paper dust and how toprotect forests in the earth. There is a trend in the world to protectthe environment of the earth, and various measures such as recycles ofcopied paper, are popularly performed in the world to reduce paper dust.One of the measures, erasable recording materials, in which images canbe reversibly recorded and erased, have been increasingly developed.

In addition, recently information processing methods have beenresearched and developed in which microcomputers having a data memoryand a display and paper are used as devices which can store and displaya variety of information such as characters and images while taking fulladvantages of the microcomputers and paper.

Japanese Laid-Open Patent Publication No. 9-101864 discloses aninformation processing apparatus which is constituted of an informationdisplaying medium which is shaped like paper and which can erasablydisplay a variety of information, an information storage medium and aninformation recording apparatus. A variety of information, e.g.,information prepared in a computer and information input by hand, can beerasably displayed in the information displaying medium. Since theinformation can be handled as digital information which can be processedby a computer, the information can be stored in the storage medium orcan be output. However, this apparatus has a drawback in that theinformation displaying medium must be set to a predetermined position,for example, by clipping, in order to make the memory or the computeroutput information as to which part in the information displaying mediuminput information is input. In other words, the precise position of theinput information in the information displaying medium cannot beidentified in such an information processing apparatus.

Japanese Laid-Open Patent Publication No. 6-222877 discloses a method inwhich at first a standard point is established by pressing a pen servingas an input device, and then the position of information is determinedas a relative position to the standard point. This proposal has anadvantage in that the apparatus has good portability because a tablet orthe like, which provides position information, is not used. However,this proposal has a drawback in that the same standard point cannot beselected in every time when the operations are repeated because anypoint in the paper can be selected as the standard point. Therefore, themethod cannot provide precise position information.

In addition, Japanese Laid-Open Patent Publication No. 8-36452 disclosesa writing pen device in which information of recorded images isdetermined using the difference in light reflection characteristicsbetween red patters and green patterns formed on the informationdisplaying paper medium. This device can provide precise positioninformation even when a user freely input information in the informationdisplaying paper medium. However, the red and green patters are notneeded for users, and in addition the patterns make informationdisplayed on the paper medium difficult to see. Further, the aestheticvalue of the information is deteriorated by the red and green patterns.Furthermore, the information displaying medium is a paper medium andtherefore cannot be reused. Therefore, the running cost is increased inthe writing pen device.

In addition, in the information processing apparatus disclosed inJapanese Laid-open Patent Publication No. 9-101864 mentioned above, whennew information is desired to be added in plural information displayingmedia having information to prepare new documents (information includingcharacters, images and the like), the new information is added thereinwhile each of the plural information displaying media is set on theinformation recording apparatus one by one, and therefore it is atroublesome operation. A method is disclosed in the publication that theold and new information in each information displaying media are storedin the information storing medium. In this method the information as toin which pages the new information has been added cannot be knownbecause each of the plural information displaying media is notidentified.

Japanese Laid-Open Patent Publication No. 7-200134 discloses a methodfor identifying an information displaying medium set on a recordingapparatus. The method is that identification information such as abarcode is printed on an upper part of each recording medium and inaddition an identification information detecting device is set to anupper part (e.g., a clipping device) of the board, on which therecording medium is to be set. However, in the method the medium is madeof paper, and therefore information cannot be reversibly recorded anderased. In addition, since the identification mark such as a barcode isprinted on the medium, the space of the medium in which informationshould be recorded is decreased. Further, the identification mark is aneyesore for persons reading the recorded information.

Japanese Laid-Open Patent Publication No. 5-124360 discloses a magneticrecording layer is additionally formed on an information displayingmedium. The information stored in the magnetic recording layer isinvisible and the space of the recording medium in which information isto be recorded is not decreased if the magnetic recording layer isformed on the back side of the displaying medium. However, if theinformation displaying medium is used in the information processingapparatus disclosed in Japanese Laid-Open Patent Publication No.9-101864, the recording apparatus becomes complex. In addition, themagnetic recording layer is troublesome to handle because the magneticrecording layer is easily affected by magnetism and therefore has to behandled carefully.

Because of these reasons, a need exists for an erasable recording systemin which information can be freely rewritten in an erasable recordingmaterial and in which additional information written on the recordingmaterial can be added in the recording material to prepare a newdocument.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide anerasable recording material in which image information is reversiblyrecorded and erased and in which additional information written on therecording material can be input to a memory storing the imageinformation previously recorded in the recording material.

Another object of the present invention is to provide an informationrecording system using the recording material, in which additionalinformation written by an inputting device on the recording material canbe incorporated in the previously recorded image information and thenthe previous image information and the additional information are outputin the recording material.

Yet another object of the present invention is to provide an informationrecording method, in which additional information written by aninputting device on the recording material can be incorporated in thepreviously recorded image information and then the previous imageinformation and the additional information are output in the recordingmaterial.

To achieve such objects, the present invention contemplates theprovision of an erasable recording material which includes a substrate,an erasable recording layer formed on the substrate and a marker (i.e.,information carrier) which is used for adding additional informationwritten on the recording layer to previously recorded information in therecording layer and a memory.

The marker is preferably invisible, or the optical density of therecording material in which the marker is present is not greater thantwice or less the optical density of the recording material in which themarker is not present. In addition, the marker is preferably detected byan optical detecting method.

The marker preferably includes an infrared absorbent selected from thegroup consisting of oxides, sulfides and halogenides and theircomplexes, which include an element selected from the group consistingof Nd, Yb, In, Sn or Zn. Alternatively the information carrier mayinclude a material which emits a fluorescent light.

The erasable recording material preferably includes an erasablethermosensitive recording layer in which visible information can bereversibly recorded and erased by changing its optical properties uponapplication of heat. The erasable thermosensitive recording layer ispreferably a layer including a leuco dye and a color developer, or alayer including a resin and a particulate organic compound having a lowmolecular weight.

The erasable recording material optionally includes an undercoat layer,an intermediate layer, and/or a protective layer. The marker may beincluded in the recording layer, undercoat layer, intermediate layerand/or protective layer, or may be formed there between or on thesubstrate. The erasable recording material may include a marker layerwhich includes a marker.

The marker may be a position information carrier or an identificationinformation carrier. In addition, the recording material of the presentinvention may include two or more markers or two or more kinds ofmarkers.

The present invention also embraces an information recording system, andan information recording method using the recording material mentionedabove.

These and other objects, features and advantages of the presentinvention will become apparent upon consideration of the followingdescription of the preferred embodiments of the present invention takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view illustrating an embodiment of the informationrecording system of the present invention;

FIG. 2 is a graph illustrating the relationship between temperature andimage density of an erasable thermosensitive recording layer for use inthe present invention in an image recording and erasing cycle;

FIG. 3 is a graph illustrating the relationship between temperature of arecording layer and transparency of another erasable thermosensitiverecording layer for use in the present invention in an image recordingand erasing cycle;

FIG. 4 is a schematic view illustrating the cross section of anembodiment of the erasable recording material of the present inventionin which a marker is included in the recording layer;

FIG. 5 is a schematic view illustrating the cross section of anotherembodiment of the erasable recording material of the present inventionin which a marker is included in the protective layer;

FIG. 6 is a schematic view illustrating the cross section of yet anotherembodiment of the erasable recording material of the present inventionin which a marker is included in the intermediate layer;

FIG. 7 is a schematic view illustrating the cross section of stillanother embodiment of the erasable recording material of the presentinvention in which a marker is included in the undercoat layer;

FIG. 8 is a schematic view illustrating the cross section of a furtherembodiment of the erasable recording material of the present inventionin which two kinds of markers are included in a layer;

FIG. 9 is a schematic view illustrating the cross section of a stillfurther embodiment of the erasable recording material of the presentinvention in which two kinds of markers are included in differentlayers;

FIG. 10 is a schematic view illustrating the cross section of a stillfurther embodiment of the erasable recording material of the presentinvention which includes a marker layer;

FIG. 11 is a schematic view illustrating the cross section of a stillfurther embodiment of the erasable recording material of the presentinvention which includes two marker layers;

FIG. 12 is a schematic view illustrating the cross section of a stillfurther embodiment of the erasable recording material of the presentinvention which includes an elastic layer.

FIG. 13 is a schematic view illustrating another embodiment of theerasable recording material having a marker in which image informationis recorded;

FIG. 14 is a schematic view illustrating another embodiment of themarker for use in the present invention;

FIG. 15 is a schematic view illustrating an image of markers picked bythe inputting device of the present invention;

FIG. 16 is a schematic view illustrating how to determine a position ofthe inputting device in the recording material;

FIG. 17 is a schematic view for explaining another position detectingmethod of the present invention;

FIG. 18 is a schematic view illustrating yet another embodiment of themarker for use in the present invention;

FIG. 19 is a schematic view illustrating an image of the mark shown inFIG. 18, which is picked by a camera of the inputting device;

FIG. 20 is a schematic view illustrating an image of markers picked by acamera of the inputting device;

FIG. 21 is a schematic view for explaining yet another positiondetecting method of the present invention;

FIG. 22 is a schematic view illustrating an embodiment of the inputtingdevice of the present invention;

FIG. 23 is a schematic view illustrating still another embodiment of themarker for use in the present invent-ion;

FIG. 24 illustrates signals obtained by scanning the marker shown inFIG. 23 with the inputting device of the present invention;

FIG. 25 is a schematic view illustrating a further embodiment of themarker for use in the present invention; and

FIG. 26 is a schematic view illustrating signals obtained by scanningthe marker shown in FIG. 25 with the inputting device of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The erasable recording material of the present invention is an erasablerecording material having an erasable recording layer, and also servesas a paper-like device having an inputting function.

The erasable recording material of the present invention at leastincludes an erasable recording layer, and a marker (i.e., an informationcarrier). The marker may be a position marker which indicates a positionin the recording material, a medium identification marker identifyingthe recording material, or a document identification marker (a pageinformation carrier) which is the address information of a document in amemory, such as name of folder, document name, page number of thedocument and the like, to identify the document. The recording materialmay include both of the position marker, the medium identificationmarker and the document identification marker.

The information recording system using the erasable recording materialof the present invention in which additional information written on therecording material is incorporated in the previously-recordedinformation to store and record together with the previously recordedimage information includes the following devices:

(1) a storage device (i.e., a memory) in which previously-recordedinformation (hereinafter sometimes referred to as memory information)and additional information written on the recording material(hereinafter referred to as added information) are stored;

(2) a controller which controls the memory information and addedinformation;

(3) an inputting device by which the added information is written on therecording material while detecting its position on the recordingmaterial using the marker and which sends the added information to areceiving device or an input port, wherein the inputting device may havea camera for detecting an optical image (a marker).

The inputting device may have a function of writing a visible image onthe recording material. If a visible image is not desired for security,the inputting device is preferably a device which does not form avisible image on the recording material.

The inputting device may have a function of heating the recordingmaterial to record a visible image in the recording layer when anerasable thermosensitive recording material is used as the recordinglayer. This inputting device is preferable because the added informationcan be erased together with the information previously-recorded in therecording material;

(4) the above-mentioned receiving device or input port which receivesthe added information transmitted by the inputting device and sends theadded information to the controller or a printing device (hereinafterboth of the receiving device and the input port are referred to thereceiving device);

(5) the above-mentioned printing device which reversibly and repeatedlyrecords the memory information and the added information in therecording material.

The information recording system may be constituted of the recordingmaterial, inputting device, receiving device, controller and storagedevice. The information recording system may include a printing device.

The information recording method in the present invention is as follows.

Information to be added to the previously-recorded image in the erasablerecording material is written with the inputting device. The addedinformation is sent to the receiving device by the inputting device.Then the receiving device sends the added information to the controlleror the printing device. The controller adds the added information to thepreviously stored information (i.e., previously-recorded information).The new information is recorded in the erasable recording material oranother erasable recording material by the printing device. When the newinformation is recorded, markers, which are used for identifyingadditional information, material identification information or documentidentification information may also be recorded in the recordingmaterial. In this case, the markers can be freely rewritten in everytime when recorded information is recorded. The markers are preferablyinvisible such that the markers do not overlap with the new information.

Hereinafter the markers used for detecting additional information aremainly explained only for explanation purposes.

The present invention will be explained in detail referring to FIG. 1.

In FIG. 1, numerals 1, 2, 3, 4, 5 and 6 denote an erasable recordingmaterial, a recorded image, markers used for detecting additionalinformation, an information inputting device (i.e., a recording pen), atrack of the pen, and a receiving device.

The recording material 1 illustrated in FIG. 1 has the image 2, but theimage 2 may not be recorded in the recording material 1. The recordingmaterial 1 set in the system illustrated in FIG. 1 is an erasablethermosensitive recording material having a recording layer whichincludes a leuco dye and a color developer and which colors and decolorsby being appropriately heated or cooled as mentioned later.

Suppose that information is additionally recorded by an inputting devicein a position of the recording material by hand and the addedinformation (the track of the inputting device) is additionally input toa memory in which the former image 2 is stored. Such recording has notbeen before.

In order to precisely input the position and the shape of the addedinformation to a memory, a start point of the inputting device must beproperly detected. The detailed description of determination of thestart point is omitted here, but for example, the following methods canbe available:

(1) A system having a recording pen having a transmitter, and a receiveris used, and the position of the recording pen is detected by thereceiving device; and

(2) A base point, which is, for example, a visible marker, is providedin the recording material 1 and the base point position is informed tothe receiver by the inputting device.

The position (x-y coordinates) of the start point of the additionalinformation relative to the base point is detected while the inputtingdevice is passing markers.

The position of the start point is transmitted to the receiving device.Then the additional information is detected as follows.

In FIG. 1, The recording material 1 has a marker such as a1, a2, a3, b1,b2 and b3, which is used for detecting additional information. Therecording pen 4 has a detecting device for detecting the marker. Forexample, the detecting device includes a light source, a light receiver,a processor and a transmitter.

After the start point is set, the information on the movement of therecording pen 4 is transmitted as the numbers that the recording pencrosses the X-axis (b1, b2, b3, . . . ) and Y-axis (a1, a2, a3, . . . )of the lattice of the marker 3. The movement of the recording pen 4 istransmitted to the receiving device 6 after every movement or after themovements are stored in a memory for a certain time. Thus the track ofthe recording pen 4, i.e., the recorded information, is input.

In addition, the information of the moving direction of the recordingpen 4 from the start point is also input by, for example, a detectingdevice at the start point. The information can be transmitted from therecording pen 4 over the air or with a wire. The markers of X-axis canbe distinguished from the Y-axis, for example, by using two kinds ofmarkers mentioned below. The information of the start point, direction,and track are received by the receiving device 6 and then sent to aprocessing device after being processed. Thus the added information iswritten in the memory in which the original image information has beenstored.

When information is recorded with the recording pen 4 on the recordingmaterial 1 having no image information, the recording material 1 servesas a simple input device and the recorded information is input to anarea of a memory having no image information or a predetermined area ofthe memory having image information. In this case, the recognition ofthe start point is not needed.

Next, another information detecting method is explained.

FIG. 13 is a schematic view illustrating another embodiment of theerasable recording material having a marker in which image informationsuch as letters and figures is recorded. In FIG. 13, numerals 1, 2, 2′and 3′ represent an erasable recording material, letter information,figure information and markers, respectively. The markers 3′ are formedto recognize added information. In this embodiment, the markers 3′ are atwo-dimensional code, i.e., a so-called QR code. The markers 3′, whichare illustrated as visible in FIG. 13 only for the explanation purpose,are preferably invisible for the reason mentioned above. The markers 3′may be formed in the entire part of the recording material as shown inFIG. 14.

The inputting device, which is shaped like a pen as shown in FIG. 17,detects its position on the recording material when additionalinformation is added, and sends the added information to the receivingdevice. The inputting device has a camera to shoot the marker. In theinputting device, a decoder which decodes the marker, and an arithmeticdevice which calculates its position by the image information in thescreen picked by the camera are provided.

FIG. 15 is a schematic view illustrating an image of markers picked byan information inputting device. The entire part of only one marker 3″is imaged in the center of the screen of the inputting device withoutomission. The absolute position of the marker is recognized by decordingthe marker' s code. In FIG. 16, the marker 3″ is represented as a box 8.Numerals 9 and 10 represent coordinates (offset coordinates) of the box8 (i.e., the marker 3″) relative to the center of the screen, that is,the position of the inputting device. Thus, the absolute position of theinputting device can be determined. This position information is sent tothe receiving device or the input port after every movement of theinputting device. The entire position information of the addedinformation may be once stored in the inputting device, and then all theposition information may be sent to the receiving device at a time.

FIG. 17 is a schematic view for explaining another position detectingmethod. In FIG. 17, numerals 3″, 4′ and 7 represent markers, anotherinputting device, and a camera. The inputting device 4′ is explainedabove. The markers 3″ are illustrated in detail in FIG. 18. As mentionedabove, the markers are preferably invisible, but is illustrated asvisible in FIGS. 17 and 18 only for the explanation purpose. In FIG. 18,the markers include first markers such as 31, 32, 33 and 34, which carryposition information, and second markers such as 31′, 32′, 33′, 34′, 35′and 36′, which surround the first markers and do not carry positioninformation.

FIG. 19 is an embodiment of the image picked by the camera in which one(the marker 31) of the first markers and four second markers (themarkers 31′, 32′, 34′ and 35′) shown in FIG. 18 are imaged on the screenof the camera. The position of the inputting device 4′ relative to thecenter of the first marker 31 can be determined by analyzing one or moreof the positions, directions and deformation degrees of the four secondmarkers 31′, 32′, 33′ and 34′. Since the absolute position of the centerof the position marker 31 can be determined by decording the positionmarker 31, the absolute position of the inputting device 4′ can bedetermined.

FIG. 20 is a schematic view illustrating an image of position markerspicked by the camera of the inputting device in another detecting methodof the present invention. In this case, there is no second marker aroundthe first markers, which is different from the markers shown in FIG. 17.As shown in FIG. 20, since there are plural markers having positioninformation in the screen, the position of the inputting device relativeto a marker, which is one of the position markers in the screen andwhich has position information, can be determined. Therefore theabsolute position of the inputting device can be determined.

FIG. 21 is a schematic view for explaining yet another positiondetecting method. Numerals 11, 12, 13 and 14 represent a recordingmaterial, an inputting device, a receiving device (or an input port),and a controller (or printer). The and added information (i.e., thetrack of the inputting device), which are detected by the inputtingdevice 12, are sent to the receiving device 13. Then the receivingdevice 13 sends the information to the controller 14. The information issent from the inputting device 12 to the receiving device 13 with orwithout a wire. When a wire is used, the information is received by theinput port 13, while the information is received by the receiving device13 in wireless transmitting.

The structure of the inputting device 12 is illustrated in detail inFIG. 22. In FIG. 22, numeral 81 represents a light source, numeral 92represents optical fibers which transmit light, numerals 94 and 95represent a first and second condensing lens, numeral 96 represents afilter, numeral 85 represents a photoreceptor, and numeral 53 representsa controller. The reference light, which is condensed by the firstcondensing lens 94, is irradiated to a marker 73. The reflected lightpasses through the optical fiber 92, and is received by thephotoreceptor 85. Thus the marker 73 is detected.

In this embodiment, the recording material has markers as shown in FIG.23, which is formed like a lattice. Each of the vertical lines and thehorizontal lines of the lattice of the markers have two or moredifferent widths, and the markers are arranged while being coded. Inaddition, the vertical lines and horizontal lines have different lightabsorption properties. In FIG. 23, only the vertical lines have twodifferent widths and are coded for preventing the drawing from beingcomplex. FIG. 24 illustrates an example of detected signals obtained byscanning the markers shown in FIG. 23 by the inputting device 12.

As can be understood from FIG. 24, the different widths of the pluralmarkers are detected. As shown in FIG. 23, the markers include widelines and narrow lines, which are arranged according to a rule, althoughthe marks seem to be arranged at random. Therefore the position of theinputting device can be determined by analyzing the signals for asampling time as shown in FIG. 24.

With respect to the horizontal lines, which have light absorptionproperties different from those of the vertical lines, the markers aresimilarly detected by using another filter suitable for detecting thehorizontal lines. Thus the horizontal lines can be detectedindependently of the vertical lines. Thus the position (track) of theinputting device can be determined.

FIG. 25 illustrates another kind of marker for use in still anotherposition detecting method of the present invention. The marker shown inFIG. 25 is observed to be similar to that shown in FIG. 23. However, themarker in FIG. 25 has different reflection densities while the marker inFIG. 23 has different widths. Although the horizontal lines of themarker have different reflection densities, the horizontal lines areillustrated by one kind of line in FIG. 25 for preventing the drawingfrom being complex. FIG. 26 is a schematic view illustrating signalsobtained by scanning marker lines shown in FIG. 25 by the inputtingdevice. The heights of signals of the marker lines depend on thereflection densities of the marker lines. Since the marker lines arearranged according to a rule, the position of the inputting device canbe determined by analyzing the detected signals for the sampling time.With respect to the horizontal marker lines, the marker is similarlydetected by using another filter as mentioned above. Thus the track ofthe inputting device can be determined, i.e., the added information canbe inputted.

The coding methods of the marker may be a so-called M-series codingmethod, which is one of coding methods.

The recording pen of the inputting device is not particularly limited.For example, a pencil, a pen, a ball-point pen, a felt-tip pen, apointer (which only traces a pattern) and the like.

When the recording material has erasable thermosensitive recording layerand the recording pen has a heating device, the added visibleinformation can be recorded in the recording material 1. It isconvenient that this added information can be erased together with theimage information previously-recorded in the recording material whilewhen the additional information is recorded with a felt-tip and thelike, the information cannot be erased together with the imagepreviously-recorded in the recording material.

The marker is not limited to a particular shape and material. Any shapesand materials which can be recognized can be used as the marker. Whenthe marker is present in the same side of the recording material onwhich the erasable recording layer is formed, it is preferable for themarker not to overlap the image information. Therefore it is preferablefor the marker to be substantially invisible. The optical density, whichis measured by Macbeth reflection densitometer RD-914, of the portion ofthe recording material in which the marker is present is twice or lessthe optical density of the portion of the recording material in whichthe marker is not present.

The marker is preferably formed of a material which can be opticallydetected and which can hardly be recognized by naked eyes. For example,materials which absorb light such as infrared light to the extent thatthe absorption of light can be detected, and materials which are exitedby absorbing light and emit fluorescent light to the extent that theemitted fluorescent can be detected, can be preferably used.

The materials which absorb light such as infrared light to the extentthat the absorption can be detected are preferably materials which haslow absorption of the visible light and can absorb light other than thevisible light. The marker is formed by a first portion which isconstituted of one or more of these materials and which absorbs specific(non-visible) light and a second portion which reflects the light.Information can be detected using the difference between the opticaldensity of the first portion and the optical density of the secondportion when measured by the specific light. In addition, since thedifference between the optical densities thereof in the visible lightregion are very little, the first portion is hardly distinguished fromthe second portion by naked eyes. Light used for detecting informationof the marker is preferably infrared light because it does notdeteriorate the materials used in the recording material unlikeultraviolet light.

Organic materials serving as such infrared light absorbents includecyanine dyes, naphthoquinone dyes, phthalocyanine dyes, anthraquinonedyes, diol dyes, triphenyl methane dyes and the like. These materialshave absorption in the visible light region, and therefore have areddish cream color. Inorganic materials, which hardly absorb visiblelight and absorb infrared light, are preferably used in the presentinvention. Suitable inorganic materials include compounds including atleast one of elements of Nd, Yb, In, Sn and Zn. In particular, themetals of the elements, and oxides, sulfides and halogenides of theelements and the like are more preferable. Since these compounds have awhite color or a pale blue color, they can be preferably used for makingthe marker invisible.

Specific examples of the compounds include ytterbium oxide, tin oxide,zinc oxide, ytterbium sulfide, zinc sulfide, ytterbium chloride, indiumchloride, tin chloride, zinc chloride, ytterbium bromide, indiumbromide, indium-tin oxides, and mixtures of an indium-tin oxide with oneof alumina, barium sulfate, silicon dioxide and calcium carbonate.

In addition, acid salts including at least one of elements of Yb, In, Snand Zn are preferable as an infrared light absorbent. Specific examplesthereof include ytterbium sulfate, zinc sulfate, indium sulfate,ytterbium nitrate, tin nitrate, ytterbium perchlorate, ytterbiumcarbonate, zinc carbonate, indium carbonate, ytterbium acetate, zincacetate, tin acetate, ytterbium nicotinate, ytterbium phosphate, zincphosphate, tin phosphate, ytterbium oxalate, zinc oxalate, tin oxalateand the like.

The materials for use in the marker, which can be excited by absorbinglight and emits fluorescent light, (hereinafter this materials arereferred to as fluorescent light emitting materials or compounds)include materials which can be recognized by the specific wavelength ofthe emitted light or the difference in strength of the emitted light.Preferably the materials are excited by infrared light and emitfluorescent light because infrared light does not deteriorate thematerials included in the recording material unlike ultraviolet light.

Organic metal compounds including at least Nd as an optical element areexemplified as the material which absorbs infrared light and emitsfluorescent light. Suitable organic compounds for use in the organicmetal compounds include carboxylic acid compounds, ketone compounds,ether compounds, amine compounds. Specific examples of the organic metalcompounds include neodymium cinnamate, neodymium naphthoate and thelike. In addition, organic metal compounds including Nd and Yb are morepreferable. Specific examples thereof include complex salts of neodymiumand ytterbium of cinnamic acid, complex salts of neodymium and ytterbiumof benzoic acid, complex salts of neodymium and ytterbium of naphthoicacid, and the like.

In addition, oxygen-including acid salt compounds including one or moreof Nd, Yb and Er can be used as the materials which absorb infraredlight and emit fluorescent light. Specific examples of oxygen-includingacid salt compounds include phosphoric acid salt compounds, vanadic acidsalt compounds, boric acid salt compounds, molybdic acid salt compoundsand the like.

Further, compounds, which include Fe and Er as optically active elementsand which include one or more elements selected from the groupconsisting of Sc, Ga, Al, In, Y, Bi, Ce, Gd, Lu and La, can also be usedas the material which absorbs infrared light and emits fluorescentlight. Furthermore, compounds, which include Yb as an optically activeelement and which include one or more elements selected from the groupconsisting of Sc, Ga, Al, In, Y, Bi, Ce, Gd, Lu and La, can also beused. In addition, organic compounds in which one or more rare earthelements selected from the group consisting of Nb, Yb and Er carry anorganic compound absorbing infrared light can also be used. Specificexamples of such organic compounds absorbing infrared light includepolymethine dyes, anthraquinone dyes, diol dyes, phthalocyanine dyes,indophenol dyes, azo dyes and the like.

The compounds mentioned above for use in the marker are used alone or incombination.

In the present invention, two or more kinds of markers can be used toprovide more precise positional information.

Plural markers can be formed, for example, by forming marker lineshaving different light absorbing properties using materials havingdifferent light absorbing properties, or by forming marker lines havinga different width.

In addition, plural markers can also be formed by forming marker lineshaving different optical properties using plural fluorescent lightemitting materials mentioned above.

Plural kinds of markers, one of which includes one or more of thematerials having light absorbing properties and another of whichincludes one or more of the fluorescent light emitting materials, arepreferably used. This type of plural kinds of markers have the followingadvantages:

(1) materials used for the plural kinds of markers can be selected fromvarious materials; and

(2) since plural information detecting methods are used, preciseposition information can be obtain.

In this type of plural markers, the markers including a fluorescentlight emitting material are preferably positioned upper than the markersincluding an infrared absorbent relative to the substrate, because ofpreventing the emitted fluorescent light from being absorbed by themarker including an infrared absorbent. The method for preparing themarkers will be described later.

In the present invention, the shape and pattern of the marker are notparticularly limited if information such as position information can beobtained by the marker.

Next, the erasable recording layer in which image information isreversibly recorded and erased will be explained.

Suitable recording methods useful for recording images in the erasablerecording layer include thermal recording, magnetic recording,photochromic recording, electrochromic recording and the like. Inparticular, thermal recording, in which visible information can berecorded and erased upon application of heat using changes of theoptical properties, is preferable. This erasable thermal recording canbe performed in the following recording layers:

(1) a layer including a leuco dye and a color developer (hereinafterreferred to as a leuco dye type recording layer);

(2) a resin layer including a particulate organic compound having a lowmolecular weight (hereinafter referred to as a transparent-opaque typerecording layer); and

(3) a layer including a low molecular weight liquid crystal compound ora high molecular weight liquid crystal compound (hereinafter referred toas a liquid crystal type recording layer).

The leuco dye type recording layer can be formed by dispersing at leasta leuco dye and a color developer in a resin binder. Suitable leuco dyesfor use in the leuco dye type recording layer include known dyeprecursors such as phthalide compounds, azaphthalide compounds, fluorancompounds, phenothiazine compounds, leuco auramine compounds and thelike. Specific examples of the leuco dyes include known materialsdescribed in Japanese Laid-Open Patent Publication No. 5-124360.

Suitable color developers for use in the leuco dye type recording layerinclude compounds having a combination of a structure, which has afunction capable of coloring the leuco dye, such as a phenolic hydroxidegroup, a carboxylic group, phosphoric group and the like, and astructure capable of controlling cohesive force of the molecules, suchas a structure having a long hydrocarbon group. The connection part ofthe structures may include a divalent group including a hetero atom. Inaddition, the long chain hydrocarbon group may include a divalent groupincluding a hetero atom or an aromatic hydrocarbon group. Specificexamples of the color developers include known color developersdescribed in Japanese Laid-Open Patent Publications Nos. 5-124360,9-290566, 9-323479, 10-67177, 10-95175 and 10-11944.

Specific examples of the resin for use as the binder resin in the leucodye type recording layer include polyvinyl chloride, polyvinyl acetate,vinyl chloride-vinyl acetate copolymers, polyvinyl acetal, polyvinylbutyral, polycarbonates, polyarylates, polysulfones, polyether sulfones,polyphenylene oxide, fluorine-containing resins, polyimides, polyamides,polyamideimides, polybenzimidazole, polystyrene, styrene copolymers,phenoxy resins, polyesters, aromatic polyesters, polyurethanes,polyacrylates, polymethacrylates, (meth)acrylic acid ester copolymers,maleic acid copolymers, epoxy resins, alkyd resins, silicone resins,phenolic resins, polyvinyl alcohols, modified polyvinyl alcohols,polyvinyl pyrrolidone, polyethylene oxide, polypropylene oxide, methylcellulose, ethyl cellulose, carboxymethyl cellulose, hydroxyethylcellulose, starch, gelatin, casein and the like.

In order to enhance the strength of the leuco dye type recording layer,one or more crosslinking agents can be added therein to crosslink thelayer. Suitable crosslinking agents include compounds having anisocyanate group, polyamide, epichlorohydrin resins, compounds having anepoxy group, glyoxal, zirconium compounds and the like.

In addition, the leuco dye type recording layer can be formed using anelectron beam crosslinking resins or an ultraviolet crosslinking resins.Suitable resins for use as the electron beam crosslinking resins orultraviolet crosslinking resins include compounds having an ethylenicunsaturated linkage.

Specific examples of the compounds include the following:

(1) poly(meth)acrylates of aliphatic, alicyclic or aromatic polyhydricalcohols, or polyalkylene glycols;

(2) poly(meth)acrylates of polyhydric alcohols in which a polyalkyleneoxide is added to an aliphatic, alicyclic or aromatic polyhydricalcohol;

(3) polyesterpoly(meth)acrylates;

(4) polyurethanepolyacrylate;

(5) epoxypoly(meth)acrylates;

(6) polyamidepoly(meth)acrylate;

(7) poly(meth)acryloyloxyalkylphosphoric acid esters;

(8) vinyl compounds or diene compounds having an (meth) acryloyl groupin their side chain or their end position;

(9) (meth)acrylate compounds, vinyl pyrrolidone compounds,(meth)acryloyl compounds having a single functional group;

(10) cyano compounds having an ethylenic unsaturated bond;

(11) mono- or polycarboxylic acids having an ethylenic unsaturated bond,and their alkali metal salts, ammonium salts, amine salts and the like;

(12) acrylamides or alkyl-substituted (meth)acrylamides having anethylenic unsaturated bond, and their polymers;

(13) vinyl lactams and polyvinyl lactams;

(14) mono- or polyethers having an ethylenic unsaturated bond, and theiresters;

(15) esters of alcohols having an ethylenic unsaturated bond;

(16) polyalcohols having an ethylenic unsaturated bond, and theiresters;

(17) aromatic compounds having one or more ethylenic unsaturated bond,such as styrene and divinyl benzene;

(18) polyorganosiloxanes having an (meth) acryloyloxy group in theirside chain or their end position;

(19) silicone compounds having an ethylenic unsaturated bond;

(20) polymers or oligoester (meth) acrylate modified compounds of thecompounds of from (1) to (19); and the like.

When the leuco dye type recording layer is formed using an ultravioletcrosslinking resin, a photo polymerization initiator is used incombination. Specific examples of the photo polymerization initiatorinclude acetophenones such as di- or trichloroacetophenone;1-hydroxycyclohexyl phenyl ketone, benzophenone, Michler's ketone,benzoin, benzoin alkyl ether, benzyl methyl ketal, tetramethylthiurammonosulfide, thioxanthones, azo compounds, diaryliodonium salts,triarylsulfonium salts, bis(trichloromethyl)triazine and the likecompounds.

The leuco dye type recording layer including one or more of these leucodyes and one or more of these color developers reversibly colors anddiscolors according to the processes as shown in FIG. 2.

In FIG. 2, when the leuco dye type recording layer which is in anon-colored state A is heated, the recording layer begins to color at atemperature not lower than an image forming temperature T1 in which atleast one of an electron donating coloring agent and an electronaccepting color developer is melted and then achieves a melted coloredstate B. If the recording layer in the melted colored state B is rapidlycooled to room temperature, the recording layer keeps the colored stateand achieves a cooled colored state C in which the electron donatingcoloring agent and the electron accepting color developer are almostsolidified. It depends upon cooling speed whether the recording layerremains in the colored state, and if the recording layer is graduallycooled, the recording layer returns to the non-colored state A (a dottedline B-A) or achieves a semi-colored state in which the image density ofthe recording layer is relatively low compared to the image density ofthe recording layer in the cooled colored state C. If the recordinglayer in the cooled colored state C is heated again, the recording layerbegins to discolor at a temperature not lower than an image erasingtemperature T2 and lower than T1 and achieves a non-colored state E (abroken line C-D-E). If the recording layer in the non-colored state E iscooled to room temperature, the recording layer returns to thenon-colored state A. The temperatures T1 and T2 depend on the materialsof the coloring agent and the color developer. Accordingly, byappropriately selecting a coloring agent and a color developer, arecording layer having desired T1 and T2 can be obtained. The imagedensities of the recording layer in the colored states B and C are notnecessarily the same.

Next, the transparent-opaque type recording layer including a resinlayer including a particulate organic compound having a low molecularweight will be explain.

The transparent-opaque type recording layer reversibly changes itstransparency. (i.e., reversibly achieves a transparent state and anopaque state) depending on the temperature of the recording layerbecause the light scattering properties of the recording layer changedepending on the temperature thereof.

Suitable resins for use in the transparent-opaque type recording layerinclude a resin which can form a layer in which low molecular weightorganic compounds are dispersed and which can maintain good transparencywhen the recording layer achieves a transparent state. Therefore theresin preferably has good transparency, mechanical stability and goodfilm forming ability. Specific examples of such a resin includepolyvinyl chloride; vinyl chloride copolymers such as vinylchloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-vinylalcohol copolymers, vinyl chloride-vinyl acetate-maleic acid copolymers,vinyl chloride-acrylate copolymers; vinylidene chloride copolymers suchas polyvinylidene chloride, vinylidene chloride-vinyl chloridecopolymers and vinylidene chloride-acrylonitrile copolymers; polyesters;polyamides; and polyacrylates, polymethacrylates and poly(meth)acrylatecopolymers; silicone resins; and the like.

Suitable low molecular weight organic materials for use in thetransparent-opaque type recording layer include a low molecular weightorganic material which is in a particulate form in the recording layerand has a melting point of from about 30 to about 200° C. and morepreferably from about 50 to about 150° C. Specific examples of the lowmolecular weight organic material include alcanols; alkane diols;halogenated alcanols and halogenated alkane diols; alkyl amines;alkanes; alkenes; alkynes; halogenated alkanes; halogenated alkenes;halogenated alkynes; cycloalkanes; cycloalkenes; cycloalkynes; saturatedor unsaturated mono- or dicarboxylic acids and their esters, amides orammonium salts; saturated or unsaturated halogenated fatty acids andtheir esters, amides or ammonium salts; allylcarboxylic acids and theiresters, amides or ammonium salts; halogenated allylcarboxylic acids andtheir esters, amides or ammonium salts; thioalcohols; thiocarboxylicacids and their esters, amides or ammonium salts; carboxylic acid estersof thioalcohol; and the like. These materials are employed alone or incombination. In addition, the carbon number of these materials is fromabout 10 to about 60, preferably from about 10 to about 38 and morepreferably from about 10 to about 30. The alcohol groups in theabove-mentioned esters may be saturated, unsaturated or halogenated. Thelow molecular weight organic materials for use in the recording layerpreferably includes at least one of groups or atoms such as —OH, —COOH,—CONH₂, —COOR, —NH—, —NH₂, —S—, —S—S—, —O—, a halogen atom or the like.

In addition, in order to broaden the temperature range in which therecording layer can achieve a transparent state, the low molecularweight organic compounds are combined with each other or other materialshaving a different melting point. The materials have been disclosed inJapanese Laid-Open Patent Publications Nos. 63-39378, 63-130380, 2-1363and 3-2089, but are not limited thereto.

The transparent-opaque type recording layer including one or more ofthese resins and one or more of these low molecular weight organicmaterials reversibly achieves a transparent state and an opaque state bythe process as shown in FIG. 3.

In FIG. 3, temperature of the recording layer is plotted along thehorizontal axis and transparency of the recording layer is plotted alongthe vertical axis. When the recording layer (in a state A) having anopaque state at room temperature of T₀ is heated to T₂, the recordinglayer achieves a transparent state (a state B). The recording layer inthe state B is cooled to room temperature, the recording layer maintainsthe transparent state (a state C). When the recording layer in the stateC is heated to a temperature above T₃, the recording layer achieves asemi-transparent state (a state D). Then the recording layer in thestate D is cooled, the recording layer does not return to thetransparent state (state C) but returns to the opaque state (state A).When the recording layer in the opaque state is heated at a temperaturebetween T₁ and T₂ and then cooled to room temperature of below T₀, therecording layer can achieve an intermediate state between thetransparent state and the opaque state.

Next, the liquid crystal type recording layer will be explained.

The liquid crystal type recording layer includes a low molecular weightor high molecular weight liquid crystal. Suitable high molecular weightliquid crystals include main chain type or side chain type liquidcrystals in which a mesogen (a molecule having liquid crystalproperties) is included in their main chain or side chain. The highmolecular weight liquid crystals are generally manufactured bypolymerizing a polymerizable mesogen compound (i.e., a mesogen monomer),or adding a reactive mesogen compound to a reactive polymer such ashydrogenated polysilicones and the like. These techniques have beendisclosed in Makromol. Chem., 179, p273 (1978), Eur. Poly. J., 18, p651(1982) and Mol. Cryst. Liq. Christ., 169, p167 (1989). The highmolecular weight crystal liquids for use in the present invention can bemanufactured by a method similar to the methods described therein.

Suitable mesogen monomers or reactive mesogen compounds includecompounds in which a group such as acrylate groups, methacrylate groupsor a vinyl group is combined, preferably through an alkyl spacer havinga predetermined length, with a rigid molecule (i.e., a mesogen) such asbiphenyl type molecules, phenylbezoate type molecules, cyclohexylbenzenetype molecules, azoxybenzene type molecules, azobenzene type molecules,azomethine type molecules, phenyl pyridine type molecules, diphenylacetylene type molecules, biphenyl benzoate type molecules,cyclohexylbiphenyl type molecules, terphenyl type molecules and thelike.

In the present invention, the marker may be formed in any position ofthe recording material, however it is preferable that the marker and theerasable recording layer are present at the same side of the substrateof the recording material. When such a recording material is used, thestructure of an information recording apparatus can be simplified ifplural recording materials are processed at the same time while beingoverlaid.

In the present invention, the marker can be formed in the erasablerecording layer. FIG. 4 is a schematic view illustrating the crosssection of an embodiment of the erasable recording material of thepresent invention having a marker therein. In FIG. 4, an erasablerecording layer 12 having a marker 13 is formed on an substrate 11.Numerals 14 and 15 denote an intermediate layer and a protective layer.

The protective layer 15 can be formed to protect the recording layer 12from being abraded. The marker 13 can be formed in the protective layer15.

FIG. 5 is a schematic view illustrating the cross section of anotherembodiment of the erasable recording material of the present inventionin which an erasable recording layer 12, an intermediate layer 14 and aprotective layer 15 are overlaid on a substrate 11 in this order,wherein a marker 13 is included in the protective layer 15. Any layerwhich substantially have no absorption in an infrared region can be usedas the protective layer 15 in the present invention, however a layermainly including a crosslinked resin is preferably used.

Crosslinked resins can be obtained by heating a mixture of acrosslinking agent and a crosslinkable resin having an active groupwhich can react with the crosslinking agent upon application of heat.

Specific examples of such a heat-crosslinkable resin include resinshaving an active group such as a hydroxy group, a carboxy group and thelike, e.g., phenoxy resins, polyvinyl butyral resins, cellulose acetatepropionate and cellulose acetate butyrate. In addition, a copolymer of amonomer having an active group such as a hydroxy group, a carboxyl groupor the like and another monomer can be employed. Specific examples ofsuch a copolymer include vinyl chloride-vinyl acetate-vinyl alcoholcopolymers, vinyl chloride-vinyl acetate-hydroxypropyl acrylatecopolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers andthe like.

Suitable crosslinking agents which can crosslink these resins uponapplication of heat include isocyanate compounds, amino resins, phenolicresins, amines, epoxy compounds and the like. For example, specificexamples of such isocyanate compounds include poly isocyanate compoundshaving plural isocyanate groups such as hexamethylene diisocyanate(HDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), andadducts of these isocyanate compounds with trimethylol propane and thelike, buret type compounds of these isocyanate compounds, isocyanuratetype compounds of these isocyanate compounds and blocked isocyanatecompounds of these isocyanate compounds.

As for the addition quantity of the crosslinking agents, the ratio ofthe number of active groups included in the resin to the number offunctional groups included in the crosslinking agent is preferably fromabout 0.01 to about 1 to maintain good heat resistance of the protectivelayer and good image formation/erasure properties of the recordinglayer.

In addition, a crosslinking promoter, which is a catalyst useful forthis kind of reaction, can also be used. Specific examples thereofinclude tertiary amines such as 1,4-diaza-bicyclo(2,2,2)octane, andmetal compounds such as organic tin compounds.

Crosslinking can also be performed upon application of an electron beamor ultraviolet light. Suitable monomers for use in electron beamcrosslinking and ultraviolet light crosslinking include the following,but are not limited thereto:

Monomers Having One Functional Group

methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butylmethacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, laurylmethacrylate, tridecyl methacrylate, stearyl methacrylate, cyclohexylmethacrylate, benzyl methacrylate, methacrylic acid, 2-hydroxyethylmethacrylate, 2-hydroxypropyl methacrylate, dimethylaminoethylmethacrylate, methyl chloride salts of dimethylaminoethyl methacrylate,diethylaminoethyl methacrylate, glycidyl methacrylate,tetrahydrofurfuryl methacrylate, allyl methacrylate, 2-ethoxyethylmethacrylate, 2-ethylhexyl acrylate, 2-ethoxyethyl acrylate,2-ethoxyethoxyethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropylacrylate, dicyclopentenylethyl acrylate, N-vinyl pyrrolidone, vinylacetate and the like.

Monomers Having Two Functional Groups

ethylene glycol dimethacrylate, triethylene glycol dimethacrylate,tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate,1,6-hexanediol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanedioldiacrylate, 1,9-nonanediol diacrylate, neopentyl glycol diacrylate,tetraethylene glycol diacrylate, tripropylene glycol diacrylate,polypropylene glycol diacrylate, diacrylate esters of an adduct ofbisphenol A with ethylene oxide, glycerin methacrylate acrylate,diacrylate esters of an adduct of neopentyl glycol with two moles ofpropylene oxide, diethylene glycol diacrylate, polyethylene glycol (400)diacrylate, diacrylate esters of an ester of hydroxy pivalate andneopentyl glycol, 2,2-bis(4-acryloyloxydiethoxyphenyl)propane, neopentylglycol diadipate diacrylate, diacrylate esters of an adduct of neopentylglycol hydroxypivalate with ε-caprolactone,2-(2-hydroxy-1,1-dimethylethyl)-5-hydroxymethyl-5-ethyl-1,3-dioxanediacrylate, tricyclodecane dimethylol diacrylate, adducts oftricyclodecane dimethylol diacrylate with ε-caprolactone, 1,6-hexanediolglycidyl ether diacrylate and the like.

Monomers Having Three or More Functional Groups

trimethylol propane trimethacrylate, trimethylol propane triacrylate,acrylate esters of an adduct of glycerin with propylene oxide,trisacryloyloxyethyl phosphate, pentaerythritol acrylate, triacrylateesters of an adduct of trimethylol propane with three moles of propyleneoxide, dipentaerythritol polyacrylate, polyacrylate esters of an adductof dipentaerythritol with ε-caprolactone, dipentaerythritol propionatetriacrylate, triacrylate esters of hydroxypivalic aldehyde modifieddimethylol propane, dipentaerythritol propionate tetraacrylate,ditrimethylol propane tetraacrylate, dipentaerythritol propionatepentaacrylate, dipentaerythritol hexaacrylate, adducts ofdipentaerythritol hexaacrylate with ε-caprolactone and the like.

Oligomers

adducts of bisphenol A with diepoxy acrylic acid and the like.

When a resin is crosslinked using ultraviolet light, one or more of thefollowing photopolymerization initiators and photopolymerizationpromoters can be used.

Specific examples of such photopolymerization initiators include:

benzoin ethers such as isobutyl benzoin ether, isopropyl benzoin ether,benzoin ethyl ether and benzoin methyl ether; α-acyloxime esters such as1-phenyl-1,2-propanedione-2-(o-ethoxycarbonyl)oxime; benzyl ketals suchas 2,2-dimethoxy-2-phenyl acetophenone and benzylhydroxycyclohexylphenyl ketone; acetophenone derivatives such asdiethoxy acetophenone and 2-hydroxy-2-methyl-1-phenylpropane-1-one; andketones such as benzophenone, 1-chlorothioxanthone,2-chlorothioxanthone, isopropylthioxanthone, 2-methylthioxanthone and2-chlorobenzophenone. These photopolymerization initiators are employedalone or in combination.

The content of the photopolymerization initiator in the recording layeror the protective layer is preferably from about 0.005 to about 1.0 partby weight, and more preferably from about 0.01 to about 0.5 part byweight, per 1 part by weight of the monomer or the oligomer.

Suitable photopolymerization promoters include aromatic tertiary aminesand aliphatic amines. Specific examples of such photopolymerizationpromoters include p-dimethylamino benzoic acid isoamyl ester,p-dimethylamino benzoic acid ethyl ester and the like. These areemployed alone or in combination. The content of the photopolymerizationpromoter in the recording layer or the protective layer is preferablyfrom about 0.1 to about 5 parts by weight, and more preferably fromabout 0.3 to about 3 parts by weight, per 1 part by weight of thephotopolymerization initiator.

Suitable light sources useful for irradiating ultraviolet light includemercury-vapor lamps, metal-halide lamps, gallium lamps, mercury-xenonlamps, flashing lamps and the like. The light source should be selectedso that the spectrum of the ultraviolet light irradiated from the lightsource corresponds to the absorption spectrum of the photopolymerizationinitiator and the photopolymerization promoter. Irradiation conditionsof ultraviolet light such as output of lamp power, irradiation width andfeeding speed (i.e., irradiation time) should be determined so that theresin used can be securely crosslinked.

Electron beam irradiation apparatus useful for crosslinking resinsincludes scanning type and non-scanning type electron beam irradiationapparatus. A suitable apparatus is selected depending on the irradiationarea and the irradiation dose required for crosslinking the layer to becrosslinked. Irradiation conditions such as electron beam current,irradiation width and irradiation speed should be determined dependingon the irradiation dose required for crosslinking the resin used.

In the present invention, an intermediate layer can be formed betweenthe recording layer and the protective layer to improve the adhesion ofthe recording layer and the protective layer, to prevent the recordinglayer from being deteriorated by coating of the protective layer coatingliquid, and to prevent the migration of the additives included in theprotective layer to the recording layer. The position informationcarrier can be formed in the intermediate layer.

FIG. 6 is a schematic view illustrating the cross section of yet anotherembodiment of the erasable recording material of the present inventionin which an erasable recording layer 12, an intermediate layer 14, and aprotective layer 15 are overlaid on a substrate 11 in this order,wherein a marker 13 is included in the intermediate layer 14. The resinsmentioned above for use in the recording layer 12 can also be used forthe intermediate layer 14.

The recording material of the present invention may include an undercoatlayer, which is heat-insulating, between the substrate and the recordinglayer to effectively utilize heat applied for recording images, toimprove the adhesion of the substrate to the recording layer, and toprevent the migration of the materials of the recording layer coatingliquid into the substrate. The heat insulating undercoat layer can beformed, for example, by coating a liquid in which organic or inorganichollow particles are dispersed in a binder resin solution. The marker 13can also be formed in the undercoat layer.

FIG. 7 is a schematic view illustrating the cross section of stillanother embodiment of the recording material of the present invention inwhich an undercoat layer 16, an erasable recording layer 12, anintermediate layer 14 and a protective layer 15 are overlaid on asubstrate 11 in this order, wherein a position information carrier 13 isformed in the undercoat layer 16.

In the present invention, additives such as fillers, lubricants,surfactants, dispersants and the like can be included in the protectivelayer 15, the intermediate layer 14, the recording layer 12 and theundercoat layer 16. Preferably the additives are materials which do notobstruct reading of the information of the marker, i.e., which do nothave absorption in infrared region.

Suitable fillers for use in the present invention include inorganicfillers and organic fillers. Specific examples of the inorganic fillersinclude carbonates such as calcium carbonate and magnesium carbonate;silicates such as silicic acid anhydride, hydrated silicic acid,hydrated aluminum silicate and hydrated calcium silicate; metalhydroxides such as aluminum hydroxide and iron hydroxide; metal oxidessuch as zinc oxide, indium oxide, alumina, silica, zirconium oxide, tinoxide, cerium oxide, iron oxide, antimony oxide, barium oxide, calciumoxide, bismuth oxide, nickel oxide, magnesium oxide, chromium oxide,manganese oxide, tantalum oxide, niobium oxide, thorium oxide, hafniumoxide, molybdenum oxide, iron ferrite, nickel ferrite, cobalt ferrite,barium titanate and potassium titanate; metal sulfides and metalsulfates such as zinc sulfide and barium sulfate; metal carbides such astitanium carbide, silicon carbide, molybdenum carbide, tungsten carbideand tantalum carbide; and metal nitrides such as aluminum nitride,silicon nitride, boron nitride, zirconium nitride, vanadium nitride,titanium nitride, niobium nitride and gallium nitride.

Specific examples of the organic fillers include silicone resins,cellulose resins, epoxy resins, nylon resins, phenolic resins,polyurethane resins, urea resins, melamine resins, polyester resins,polycarbonate resins, styrene resins such as polystyrene resins,styrene-isoprene copolymers and styrene-vinyl benzene copolymers;acrylic resins such as vinylidene chloride-acryl copolymers,acryl-urethane copolymers and ethylene-acryl copolymers; polyethyleneresins, formaldehyde resins such as benzoguanamine-formaldehyde resinsand melamine-formaldehyde resins; and polymethyl methacrylate resins andvinyl chloride resins.

These fillers can be used alone or in combination. In addition, thefillers may be complex particles. The fillers may have any shape such asspherical, granular, plate and needle shapes.

The content of the filler in each layer is preferably from 1 to 95% byvolume, and more preferably from 5 to 75% by volume.

Specific examples of the lubricants for use in the present inventioninclude synthesized waxes such as ester waxes, paraffin waxes andpolyethylene waxes; vegetable waxes such as hardened caster oil; animalwaxes such as hardened beef tallow; higher alcohols such as stearylalcohol and behenyl alcohol; higher fatty acids such as margaric acid,lauric acid, myristic acid, palmitic acid, stearic acid, and behenicacid; esters of higher fatty acids such as sorbitan fatty acid esters;and amides such as stearic acid amide, oleic acid amide, lauric acidamide, ethylenebisstearic acid amide, methylenebisstearic acid amide andmethylolstearic acid amide.

The content of the lubricants in each layer is preferably from 0.1 to95% by volume, and more preferably from 1 to 75% by volume.

The intermediate layer and protective layer may include an organicultraviolet absorbing agent in an amount of from 0.5 to 10 parts byweight per 100 parts by weight of the binder resin included therein.

Specific examples of the organic ultraviolet absorbing agent include:

Benzotriazole Type Ultraviolet Absorbing Agents

2-(2′-hydroxy-5′-methylphenyl)benzotriazole,

2-(2′-hydroxy-5′-t-butylphenyl)benzotriazole,

2-(2′-hydroxy-3′,5′-di-t-butylphenyl)benzotriazole,

2-(2′-hydroxy-3′-t-butyl-5′-methylphenyl)benzotriazole,

2-(2′-hydroxy-5′-octoxyphenyl)benzotriazole,

2-(2′-hydroxy-3′,5′-di-t-butylphenyl)-5-chlorobenzotriazole,

2-(2′-hydroxy-3′-t-butyl-5′-methylphenyl)-5-chlorobenzotriazole, and

2-(2′-hydroxy-5′-ethoxyphenyl)benzotriazole.

Benzophenone Type Ultraviolet Absorbing Agents

2,4-dihydroxybenzophenone,

2-hydroxy-4-methoxybenzophenone,

2-hydroxy-4-n-octoxybenzophenone,

2-hydroxy-4-dodecyloxybenzophenone,

2,2′-dihydroxy-4-methoxybenzophenone,

2,2′-dihydroxy-4,4′-dimethoxybenzophenone,

2,2′,4,4′-tetrahydroxybenzophenone,

2-hydroxy-4-methoxy-2′-carboxybenzophenone,

2-hydroxy-4-oxybenzylbenzophenone,

2-hydroxy-4-chlorobenzophenone,

2-hydroxy-4-methoxybenzophenone-5-sulfonic acid,

2-hydroxy-4-methoxybenzophenone-5-sulfonic acid sodium salt, and

2,2-dihydroxy-4,4′-dimethoxybenzophenone-5-sulfonic acid sodium salt.

Salicylic Acid Ester Type Ultraviolet Absorbing Agents

phenyl salicylate,

p-octylphenyl salicylate,

p-t-butylphenyl salicylate,

carboxyphenyl salicylate,

methylphenyl salicylate,

dodecylphenyl salicylate,

2-ethylhexylphenyl salicylate, and

homomenthylphenyl salicylate.

Cyanoacrylate Type Ultraviolet Absorbing Agents

2-ethylhexyl-2-cyano-3,3′-diphenyl acrylate, and

ethyl-2-cyano-3,3′-diphenyl acrylate.

p-aminobenzoic Acid Type Ultraviolet Absorbing Agents

p-aminobenzoic acid,

glyceryl p-aminobenzoate,

amyl p-dimethylaminobenzoate, and

ethyl p-dihydroxypropylbenzoate.

Cinnamic Acid Type Ultraviolet Absorbing Agents

2-ethylhexyl p-methoxycinnamate, and

2-ethoxyhexyl p-methoxycinnamate.

Other Ultraviolet Absorbing Agents

4-t-butyl-4′-methoxy-dibenzoyl methane

urocanic acid,

ethyl urocanate, and the like.

In the present invention, two or more markers can be included in therecording material. FIG. 8 is a schematic view illustrating the crosssection of a further embodiment of the recording material of the presentinvention in which two markers 13 and 13 b are included in theintermediate layer 14. Plural markers 13 and 13 b may be included in therecording layer 12, the protective layer 15 or the undercoat layer 16 aswell as in the intermediate layer 14.

In addition, plural markers can be included in the recording materialsuch that the markers are included in plural layers. FIG. 9 is aschematic view illustrating a still further embodiment of the recordingmaterial of the present invention in which two markers 13 and 13 b areincluded in the intermediate layer 14 and the protective layer 15,respectively. The markers 13 and 13 b can be included in any differentlayers as well as in the intermediate layer 14 and the protective layer15.

In the present invention, the marker may be formed as a marker layerwhich includes one or more kinds of markers. FIG. 10 is a schematic viewillustrating the cross section of a still further embodiment of thepresent invention in which an erasable recording layer 12, a markerlayer 17, an intermediate layer 14 and protective layer 15 are overlaidon a substrate 11 in this order. The marker layer 17 can be formed atany position, but the layer 17 is preferably formed at a position upperthan the recording layer 12 relative to the substrate 11 to obtain anadvantage in that information therein can be clearly recognized.

Plural marker layers can also be formed in the recording material of thepresent invention. FIG. 11 is a schematic view illustrating the crosssection of a still further embodiment of the recording material of thepresent invention in which two marker layers 17 and 17 b are formedbetween the recording layer 12 and the intermediate layer 14.

The recording material of the present invention may include an elasticlayer to prevent formation of uneven images in the recording layer.

FIG. 12 is a schematic view illustrating the cross section of a stillfurther embodiment of the recording material of the present invention inwhich an elastic layer 18, an erasable recording layer 12 including amarker 13, an intermediate layer 14 and a protective layer 15 areoverlaid on a substrate 11 in this order.

When the elastic layer 18 is formed, asperities of the surface of therecording material, which is caused by formation of the positioninformation carrier and which cause formation of uneven images in therecording layer, can almost be flattened when images are formed, forexample, using a thermal head. This is because when a pressure isapplied to form images, the elastic layer deforms at the position onwhich the marker is formed.

Specific examples of the materials for use in the elastic layer includematerials such as silicone rubbers, butadiene rubbers, urethane rubbers,isoprene rubbers, nitrile-butadiene rubbers, highly-satuated nitrilerubbers, ethylene-propylene rubbers, fluorine-containing rubbers,styrene-butadiene rubbers, chloroprene rubbers, acrylic rubbers,chlorosulfonated polyethylene rubbers, chlorinated polyethylene rubbers,ethylene-acryl rubbers, epichlorohydrin rubbers, polysulfide rubbers,ultraviolet crosslinking resins having elastic properties, and the like.

In the present invention, micro hollow particles can be used to form theelastic layer 18. The micro hollow particles are materials in which airand/or other gasses are included in a shell made of a thermoplasticresin. Specific examples of the thermoplastic resins for use as theshell include polystyrene, polyvinyl chloride, polyvinylidene chloride,polyvinyl acetate, polyacrylic acid esters, polyacrylonitrile,polybutadiene, and their copolymers and the like. Among these resins,copolymers mainly constituted of vinylidene chloride and acrylonitrileare preferable.

In the present invention, the marker can be formed by one or moreprinting or recording methods such as gravure printing, screen printing,rotary screen printing, offset printing, thermal transfer recording,electrophotographic recording, ink jet printing and the like. The ink ortoner used for forming the marker preferably includes a high molecularweight binder resin.

The recording material of the present invention is preferablysheet-shaped, card-shaped or label-shaped.

Hereinbefore, the present invention is explained referring to theposition marker, however the identification marker can also be formedusing the materials and methods similar to those mentioned above. Whenadditional information written on the recording material is input, atfirst the position in a memory, in which the additional information isto be stored, is determined using the medium identifying marker and thedocument identifying marker. Then the additional information is storedin the position of the memory. The identification marker includes, forexample, one or more of barcodes, marks, pictures, characters and thelike.

Having generally described this invention, further understanding can beobtained by reference to certain specific examples which are providedherein for the purpose of illustration only and are not intended to belimiting. In the descriptions in the following examples, the numbersrepresent weight ratios in parts, unless otherwise specified.

EXAMPLES Example 1

(Method for Forming Undercoat Layer)

A mixture of the following components was pulverized and dispersed usinga ball mill to prepare an undercoat layer coating liquid.

(Formulation of undercoat layer coating liquid) heat-expansible finehollow particles 15 (Micropearl F-30, manufactured by Matsumoto YushiSeiyaku Co., Ltd.) Polyvinyl butyral 5 Ethyl alcohol 70 Toluene 30

An undercoat layer was formed with a wire bar by coating the undercoatlayer coating and then drying the coated liquid.

(Formation of Erasable Thermosensitive Recording Layer)

A mixture of the following components was pulverized and dispersed usinga ball mill to prepare an erasable thermosensitive recording layercoating dispersion.

(Formulation of erasable thermosensitive recording layer coatingdispersion) 2-anilino-3-methyl-6-dibutylaminofluoran 2N-(4-hydroxyphenyl)-6-(N′-octadecylureido)hexaneamide 8 Acryl polyolresin solution of tetrahydrofuran 70 (solid content of 15% by weight)

Ten (10) parts of Coronate HL manufactured by Nippon PolyurethaneIndustry Co., Ltd. (an ethyl acetate solution of an adduct typehexamethylene diisocyanate, solid content of 75%) were added to the thusprepared dispersion, and the mixture was mixed well to prepare anerasable thermosensitive recording layer coating liquid (i.e., a leucodye type recording layer coating liquid).

An erasable thermosensitive recording layer was formed by coating therecording layer coating liquid with a wire bar, drying the coated liquidat 100° C. for 2 minutes and then heating the formed layer at 60° C. 24.

(Method for Forming Intermediate Layer)

The following components were mixed to prepare an intermediate layercoating liquid.

Acryl polyol solution of methyl ethyl ketone 30 (Viosorb 130manufactured by Kyodo Chemical Co., Ltd., solid content of 15%)(2-hydroxy-4-n-octoxy)benzophenon 4 Coronate HL 4

An intermediate layer was formed by coating the intermediate layercoating liquid with a wire bar, drying the coated liquid at 100° C. for2 minutes and then heating the formed layer at 60° C. 24 hours.

(Method for Forming Protective Layer)

The following compounds were mixed to dissolve the resin and to preparea protective layer coating liquid.

Urethane-acrylate type ultraviolet crosslinking resin 15 (C7-157manufactured by Dainippon Ink and Chemicals, Inc.) Ethyl acetate 85

A protective layer was formed by coating the protective layer coatingliquid with a wire bar, drying the coated liquid at 90° C. for 1 minuteand then feeding the formed layer under an ultraviolet lamp havingirradiation energy of 80 W/cm at a speed of 9 m/min so that the layerwas crosslinked.

(Method for Forming Elastic Layer)

The following components were mixed to prepare an elastic layer coatingliquid.

Butadiene resin 10 (JSR BR820 manufactured by Japan Synthetic RubberCo., Ltd.) Toluene 10

An elastic layer was formed by coating the elastic layer coating liquidwith a wire bar and drying the coated liquid.

(Method for Forming Marker)

The following components were mixed using an attritor including glassbeads to prepare an ink for use in an ink ribbon.

Ytterbium sulfate 3 Wax 5

The ink was coated by gravure coating on a polyethylene terephthalatefilm (PET film) having a thickness of 4 μm to prepare an ink ribbon.

A lattice pattern, which was a marker, was formed bythermally-transferring the ink of the ink ribbon using a thermaltransfer recording method.

(Method for Forming Recording Material)

Some of these layers mentioned above, and the marker were formed on awhite polyester film having a thickness of 100 μm to prepare erasablethermosensitive recording materials of Examples 1-1 to 1-7. At thispoint, the thickness of each layer was 5 μm on a dry basis. Thestructures of the recording materials are described below, whereincharacters S, M, UL, RTRL, IL, PL and EL represent the substrate, themarker, the undercoat layer, the erasable thermosensitive recordinglayer, the intermediate layer, the protective layer and the elasticlayer, respectively.

Example 1-1

S/M/RTRL/IL/PL

Example 1-2

S/RTRL/M/IL/PL

Example 1-3

S/RTRL/IL/M/PL

Example 1-4

S/M/UL/RTRL/IL/PL

Example 1-5

S/M/RTRL/EL/PL

Example 1-6

S/RTRL/IL/M/EL/PL

Example 1-7

S/RTRL/IL/PL/M/EL

In addition, a marker layer was formed by printing the informationcarrier, and then coating thereon an intermediate layer coating liquidand drying the coated intermediate layer coating liquid such that thecoated intermediate layer had the same thickness as that of the marker.

The following erasable thermosensitive recording materials of Examples1-8 to 1-10 were prepared. At this point, character ML represents amarker layer.

Example 1-8

S/ML/RTRL/IL/PL

Example 1-9

S/RTRL/ML/IL/PL

Example 1-10

S/RTRL/IL/ML/PL

A portion in each of the thus prepared erasable thermosensitiverecording materials in which the marker was present could hardly bedistinguished by naked eyes from a portion in the erasablethermosensitive recording material in which the marker was not present.

In addition, the recording materials of Examples 1-1 to 1-10 weresubjected to a test for reading the information of the marker using aninfrared light emitting diode as a light source and a CCD linear sensoras a light receiving element.

The results are shown in Table 2, wherein a circle mark (◯) means thatthe information can be read and a cross mark (×) means that theinformation cannot be read.

TABLE 2 Ex. No. 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-8 1-9 1-10 Test ◯ ◯ ◯ ◯ ◯◯ ◯ ◯ ◯ ◯ results

An image (memory information) was recorded in each recording layer ofthe erasable thermosensitive recording materials of Examples 1-1 to 1-10using a thermal head. Then the recording materials having an image werealso subjected to the reading test mentioned above.

The results are shown in Table 3.

TABLE 3 Ex. No. 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-8 1-9 1-10 Test ◯ ◯ ◯ ◯ ◯◯ ◯ ◯ ◯ ◯ results

Then the image was erased by heating for 1 second each recordingmaterial with a block heated at 120° C. The image in each recordinglayer was perfectly erased, and the recording materials returned to theformer white recording material. The white recording materials in whichthe image had been erased were subjected to the reading test mentionedabove.

The results are shown in Table 4.

TABLE 4 Ex. No. 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-8 1-9 1-10 Test ◯ ◯ ◯ ◯ ◯◯ ◯ ◯ ◯ ◯ results

This cycle of operations of image recording, information reading, imageerasing, and information reading was repeated 5 times. The recordingmaterials in which a 5^(th) image was formed and the white recordingmaterials in which the 5^(th) image had been erased were also subjectedto the test for reading the information.

The results are shown in Table 5.

TABLE 5 Ex. No. 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-8 1-9 1-10 Reading ◯ ◯ ◯ ◯◯ ◯ ◯ ◯ ◯ ◯ test for image recorded recording material Reading ◯ ◯ ◯ ◯ ◯◯ ◯ ◯ ◯ ◯ test for image erased recording material

The image qualities of the images repeatedly formed in the recordingmaterials of Examples 1-1 to 1-10 were the same as those of the firstimage thereof. Therefore it is confirmed that the recording materialscan be repeatedly used.

Example 2

The procedure for preparation of the erasable thermosensitive recordingmaterials of Examples 1-1 to 1-10 was repeated except that the thermaltransfer ribbon used for recording the marker was prepared as follows.

Twenty (20) parts of a neodymium/ytterbium complex salt of cinnamic acidwere suspended in 400 parts of water. A solution in which 0.06 parts ofa polymethine dye (trade name of IR-820B, manufactured by Nippon KayakuCo., Ltd.) were dissolved in 20 parts of dimethylformamide was droppedin the suspension prepared above. After 1 hour stirring, the mixture wasfiltered and the filtered cake was dried. Fifteen (15) parts of thedried cake were mixed together with 3 parts of a wax, 1 part ofpolyester resin and 1 part of polyurethane resin, and dispersed toprepare an ink for thermal transfer recording. The ink was coated on apolyethylene terephthalate film (PET film) having a thickness of 4.0 μmand dried to prepare a thermal transfer ribbon.

Thus, thermosensitive recording materials of Examples 2-1 to 2-10 of thepresent invention were prepared.

A portion in each of the thus prepared erasable thermosensitiverecording materials in which the marker was present could hardly bedistinguished by naked eyes from a portion in the erasablethermosensitive recording material in which the information carrier wasnot present.

The optical density of the portion having a marker (i.e., informationrecorded area) and the portion having no marker (i.e., background area)was measured with a reflection densitometer, RD-914 manufactured byMacbeth Co. The results are shown in table 6.

TABLE 6 Ex. No. 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 Optical 0.080.09 0.10 0.09 0.09 0.09 0.10 0.08 0.09 0.10 density of informationrecorded area Optical 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08density of background area

In addition, the marker was read with a handy scanner LM-R-600(manufactured by Hitachi-Maxell Ltd.) used for reading Stealth barcodes.The results are shown in Table 7. The circle mark (◯) means that theinformation of the marker can be read and the cross mark (×) means thatthe information cannot be read.

TABLE 7 Ex. No. 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 Readability ◯ ◯◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯

An image was formed in each recording layer of the erasablethermosensitive recording materials of Examples 2-1 to 2-10 using athermal head. Then the recording materials having an image weresubjected to the reading test mentioned above.

The results are shown in Table 8.

TABLE 8 Ex. No. 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 Readability ◯ ◯◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯

Then the image was erased by heating for 1 second each recordingmaterial with a block heated at 120° C. The image in each recordinglayer was perfectly erased, and the recording materials returned to theformer white recording material. The white recording materials in whichthe image had been erased were subjected to the reading test mentionedabove.

The results are shown in Table 9.

TABLE 9 Ex. No. 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 Readability ◯ ◯◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯

This cycle of operations of image recording, position informationreading, image erasing, and position information reading was repeated 5times. The recording materials in which a 5^(th) image was formed andthe white recording materials in which the 5^(th) image had been erasedwere subjected to the test for reading the marker.

The results are shown in Table 10.

TABLE 10 Ex. No. 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 Reading ◯ ◯ ◯◯ ◯ ◯ ◯ ◯ ◯ ◯ test for image recorded recording material Reading ◯ ◯ ◯ ◯◯ ◯ ◯ ◯ ◯ ◯ test for image erased recording material

The image qualities of the images repeatedly formed in the recordingmaterials of Examples 2-1 to 2-10 were the same as those of the firstimage thereof. Therefore it is confirmed that the recording materialscan be repeatedly used.

Example 3

Erasable thermosensitive recording materials of the present invention ofExamples 3-1 to 3-3 were prepared in the same way as performed inExample 1 using the coating liquids prepared in Example 1 such that thelayer thickness of each layer was 5 μm and the layers were overlaid asdescribed below. In example 3, the lattice of the marker, which wasformed in the same way as performed in Example 1, was used as X-axis andY-axis.

Example 3-1

S/M-1/M-2/ETRL/IL/PL

Example 3-2

S/ETRL/M-1/M-2/IL/M/PL

Example 3-3

S/M-1/ETRL/M-2/M/IL/PL

Example 3-4

S/ETRL/ML-1/ML-2/IL/PL

Example 3-5

S/ML-1/ETRL/ML-2/IL/PL

In the structures mentioned above, M-1 and M-2 represent a marker formedusing the thermal transfer ribbon prepared in Examples 1 and 2,respectively. In addition, ML-1 and ML-2 represent a Marker layer, whichwas formed in the same way as performed in Examples 1 and 2.

A portion in each of the thus prepared erasable thermosensitiverecording materials in which the information was present could hardly bedistinguished by naked eyes from a portion in the erasablethermosensitive recording material in which the information was notpresent.

In addition, the recording materials of Examples 3-1 to 3-5 weresubjected to the reading test for reading the information of the markerusing an infra-red light emitting diode as a light source and a CCDlinear sensor as a light receiving element, and the reading test using ahandy scanner LM-R-600 (manufactured by Hitachi-Maxell Ltd.) used forreading Stealth barcodes.

The results are shown in Table 11, wherein a circle mark (◯) representsthat the information can be read in both reading tests and a cross mark(×) represents that the information cannot be read in both readingtests.

TABLE 11 Ex. No. 3-1 3-2 3-3 3-4 3-5 Readability ◯ ◯ ◯ ◯ ◯

An image was formed in each recording layer of the erasablethermosensitive recording materials of Examples 3-1 to 3-5 using athermal head. Then the recording materials having an image weresubjected to the reading test mentioned above.

The results are shown in Table 12.

TABLE 12 Ex. No. 3-1 3-2 3-3 3-4 3-5 Readability ◯ ◯ ◯ ◯ ◯

Then the image was erased by heating for 1 second each recordingmaterial with a block heated at 120° C. The image in each recordinglayer was perfectly erased, and the recording materials returned to theformer white recording material. The white recording materials in whichthe image had been erased were subjected to the test mentioned above.

The results are shown in Table 13.

TABLE 13 Ex. No. 3-1 3-2 3-3 3-4 3-5 Readability ◯ ◯ ◯ ◯ ◯

This cycle of operations of image recording, information reading, imageerasing, and information reading was repeated 5 times. The recordingmaterials in which a 5^(th) image was formed and the white recordingmaterials in which the 5^(th) image had been erased were subjected tothe test for reading the information.

The results are shown in Table 14.

TABLE 14 Ex. No. 3-1 3-2 3-3 3-4 3-5 Reading test for ◯ ◯ ◯ ◯ ◯ imagerecorded recording material Reading test for ◯ ◯ ◯ ◯ ◯ image erasedrecording material

The image qualities of the images repeatedly formed in the recordingmaterials of Examples 3-1 to 3-5 were the same as those of the firstimage thereof. Therefore it is confirmed that the recording materialscan be repeatedly used.

As can be understood from the above description, the erasablethermosensitive recording material of the present invention canrepeatedly record an image and erase the image, and in addition caninput additional information written thereon to a memory in which theprevious image information is stored.

Additional modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced other than as specifically described herein.

This document claims priority and contains subject matter related toJapanese Patent Applications Nos. 10-374018 and 10-376915, both of whichare filed on Dec. 28, 1998, 11-025720 filed on Feb. 3, 1999, and11-142813 filed on May 24, 1999, the entire contents of which are hereinincorporated by reference.

What is claimed is:
 1. An information recording method comprising thesteps of: providing an erasable recording material comprising asubstrate, an erasable recording layer which is formed overlying thesubstrate and in which image information is repeatedly recorded anderased, and one or more markers; recording memory information stored ina memory in the recording layer; writing additional image information onthe recording material with an inputting device while detectingpositions of the inputting device; transmitting the additional imageinformation; and storing the additional image information in the memory.2. The information recording method according to claim 1, wherein themethod further comprises the steps of: secondly recording the memoryinformation and the additional image information in the recording layer.3. The information recording method according to claim 2, wherein therecording step and secondly recording step further comprises recording amarker in the recording layer.
 4. The information recording methodaccording to claim 1, wherein the additional image information writtenon the image information recording material is visible.
 5. Theinformation recording method according to claim 1, wherein at least oneof the one or more markers comprises absolute position information, andwherein the position of the inputting device is detected by acombination of at least one of a position, a direction and deformationof the optically read marker or markers with the absolute positioninformation.
 6. The information recording method according to claim 1,wherein the recording material comprises at least one first marker andplural second markers, wherein the first marker comprises absoluteposition information and the second markers are disposed around thefirst marker, and wherein the position of the inputting device isdetected by a combination of at least one of information selected fromthe group consisting of a position, a direction and deformation of theoptically read second markers with the absolute position information ofthe first marker.
 7. The information recording method according to claim1, wherein the recording material comprises plural markers including atleast one first marker comprising absolute position information and atleast one second marker, and wherein the position of the inputtingdevice is detected by a combination of at least one of informationselected from the group consisting of a position, a direction anddeformation of the optically read markers with the absolute positioninformation of the first marker.
 8. The information recording methodaccording to claim 1, wherein the one or more markers comprises alattice marker including coded vertical lines and coded horizontallines, and wherein the position of the inputting is detected by decodingthe vertical lines and the horizontal lines.
 9. The informationrecording method according to claim 8, wherein each of the verticallines and the horizontal lines have two or more different widths. 10.The information recording method according to claim 8, wherein each ofthe vertical lines and the horizontal lines have two or more differentoptical densities.
 11. The information recording method according toclaim 8, wherein the vertical lines and the horizontal lines are codedaccording to an M-series coding method.
 12. An information recordingmethod comprising the steps of: providing an erasable recording materialcomprising a substrate, an erasable recording layer which is formedoverlying the substrate and in which image information is repeatedlyrecorded and erased, and one or more markers; and writing imageinformation on the recording material with an inputting device whiledetecting a position of the inputting device by optically reading atleast one of the one or more markers.
 13. An inputting device forinputting an image information written on an erasable recording materialhaving one or more markers comprising: a writing head by which the imageinformation is written on the erasable recording material; and anoptically position-detecting element which detects a position thereof.14. The inputting device according to claim 13, wherein an imageinformation written by the writing head is visible.
 15. The inputtingdevice according to claim 14, wherein the erasable recording materialcomprises an erasable thermosensitive recording layer, wherein thewriting device comprises a heat source to heat the writing head to formthe image information in the erasable thermosensitive recording layer.16. The inputting device according to claim 13, wherein the opticallyposition-detecting element comprises a camera.
 17. The inputting deviceaccording to claim 13, wherein the optically position-detecting elementcomprises a light source and a photoreceptor.